1) Field of the Invention
The present invention relates to novel quinolone derivatives and salts thereof, which are useful as synthetic antibacterial agents, to preparation processes thereof and also to antibacterial agents containing the same.
2) Description of the Related Art
Many of compounds having pyridonecarboxylic acid as a basic skeleton are known to be useful as synthetic antibacterial agents for their excellent antibacterial activities and broad antibacterial spectrum. Among these, norfloxacin [Japanese Patent Application Laid-Open (Kokai) No. 141286/1978], enoxacin [Japanese Patent Application Laid-Open (Kokai) No. 31042/1980], ofloxacin [Japanese Patent Application Laid-Open (Kokai) No. 46986/1982], ciprofloxacin [Japanese Patent Application Laid-Open (Kokai) No. 76667/1983] and the like have already found wide-spread clinical utility as therapeutic agents for infectious diseases.
Principal features of these compounds reside in that the quinoline skeleton or naphthyridine skeleton is substituted on position 6 with a fluorine atom and a secondary amino group is contained at position 7. In particular, the introduction of a piperazine ring or pyrrolidine ring to position 7 is considered to play a significant role in the enhancement of antibacterial activities.
However, these compounds are still not fully satisfactory in antibacterial activities, intestinal absorption, metabolic stability, or side effects, etc. There is an outstanding desire for the preparation of novel compounds which can satisfy these requirements.